JP4593809B2 - Piezoelectric device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric device, and more particularly to a piezoelectric device composed of a piezoelectric vibrator or an IC chip used for mobile communication equipment or the like.
[0002]
[Prior art]
As for a crystal oscillator as an example of a conventional piezoelectric device, a structure as shown in FIGS. 6 to 7 has already been known (see Japanese Patent Laid-Open No. 2000-278047).
[0003]
The crystal oscillator 51 is mainly composed of a ceramic package 52 having a cavity on both sides, a crystal resonator 53, a conductive adhesive member 54, a flat substrate 57, and an IC chip 58.
In the quartz resonator 53, excitation electrodes 53b are attached to both main surfaces of a strip-like quartz substrate 53a. Further, an extraction electrode 53c extending from each excitation electrode was attached to one short side of the quartz substrate 53a.
[0004]
The ceramic package 52 is formed by stacking dielectric substrates 521a and 521b such as alumina, and a seal ring 523 for forming a cavity 520a is formed on one main surface in the stacking direction. In one cavity 520 a, a crystal resonator 53 is accommodated in an electrode pad 524 formed on the bottom surface so that a lead electrode 53 c is placed, and is fixed and connected by a conductive adhesive member 54, and is made of metal on a seal ring 523. The cavity 56a is hermetically sealed by the seam welding of the lid 56.
[0005]
Further, on the opening end face of the other cavity 520b, an electrode pad led out from an electrode pad 524 to which the above-described crystal resonator 53 is connected by a lead electrode 53c and an electrode pad connected to GND are formed.
[0006]
As described above, the ceramic package 52 has a substrate structure (hereinafter, referred to as “H-type structure”) having a H-shaped cross section.
[0007]
Further, a wiring pattern is formed on the flat substrate 57, and an electronic component element 59 such as an IC chip 58 or a capacitor is mounted and connected thereto. Further, the filling resin 570 is filled on the IC chip 58 and the electronic component 59 so as to cover the whole.
[0008]
The above-described crystal resonator 53, IC chip 58, and electronic component element 59 are formed on a predetermined wiring pattern (not shown) formed on one end of the ceramic package 52 from the main surface of the ceramic package 52 or on a flat substrate. An oscillation circuit is formed by connecting with a predetermined wiring pattern (not shown), and is extended to an external terminal electrode 571 formed on the lower surface of the flat plate upper substrate 57.
[0009]
[Problems to be solved by the invention]
However, there have been the following problems. That is, as shown in FIGS. 6 to 7, the conventional crystal oscillator 51 is not formed with a member that gives a shielding effect to the dielectric substrate 521 a on the bottom surface of the ceramic package 52. 53 is susceptible to electromagnetic influence from the oscillation circuit via the ceramic package 52, and the oscillation circuit itself is likely to have electromagnetic influence on the outside.
[0010]
The present invention has been devised in view of the above-described problems, and its object is to enhance the shielding effect of the piezoelectric vibrator and the oscillation circuit of the piezoelectric device individually, and to stabilize the electrical characteristics such as the oscillation frequency for reliability. It is an object of the present invention to provide a piezoelectric device capable of improving the productivity and improving the mass productivity and the yield.
[0011]
[Means for Solving the Problems]
According to one aspect of the present invention, a piezoelectric device includes a rectangular container having a cavity formed on one main surface, a plurality of electrode pads formed on the bottom surface of the cavity, and a pair of electrodes connected to the electrode pads. A piezoelectric vibrator mounting substrate having a piezoelectric vibrator having an excitation electrode formed thereon, a metal lid for sealing the cavity, a rectangular container having a cavity formed on one main surface, and the cavity An oscillation circuit board having an internal wiring formed on the bottom surface and an electronic component connected to the internal wiring and driving the piezoelectric vibrator, and one main surface side of the piezoelectric vibrator mounting board and the oscillation The one main surface side of the circuit board is electrically and mechanically connected to each other, and the metal lid is connected to the ground potential. The container of the piezoelectric vibrator mounting board is a ring-shaped first. Before the board A ring-shaped second substrate having a larger inner periphery than the first substrate and having a narrow width, and the oscillation circuit substrate has a ring-shaped third substrate having a smaller inner periphery and a wider width than the second substrate. The metal lid is surrounded by the second substrate and located between the first substrate and the third substrate.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a piezoelectric device of the present invention will be described in detail with reference to the drawings.
1 is a side sectional view of a piezoelectric device according to the present invention, FIG. 2 (a) is a side sectional view of only a crystal resonator mounting substrate used in the piezoelectric device, and FIG. 1 (b) is a side view of only an oscillation circuit substrate. 3 is a top view and a bottom view in which the metal lid of the crystal unit is omitted, and FIG. 4 is a top view and a bottom view of an oscillation circuit board used in the piezoelectric device.
In the following description, a crystal oscillator is used as the piezoelectric device, and an example in which a crystal oscillator is used will be described. In addition, the piezoelectric device of the present invention includes other piezoelectric ceramic substrates other than crystal oscillators, piezoelectric vibrators using single crystal piezoelectric substrates, and piezoelectric devices composed of piezoelectric vibrators.
[0017]
A crystal oscillator 1 according to the present invention includes a container-shaped crystal resonator mounting substrate 2 on which a crystal resonator is mainly mounted, a container-shaped oscillation circuit substrate 7 in which an IC chip 8 and an electronic component 9 are accommodated, and a metal lid 6. It is composed of
[0018]
The crystal resonator mounting substrate 2 includes a plate-shaped dielectric substrate 21, a ring-shaped dielectric substrate 22 provided around the dielectric substrate 21, and a ring-shaped dielectric having a larger inner circumference and a narrower width than the dielectric substrate 22. A body substrate 23 is laminated and formed on the outer peripheral portion of the upper surface of the dielectric substrate 22, and a sealing conductor 221 is deposited on the inner peripheral surface of the upper surface of the dielectric substrate 22.
[0019]
Between the laminated dielectric substrate 21 and the dielectric substrates 22 and 23, an internal wiring pattern (not shown) and a via hole conductor that penetrates the ceramic substrate in the thickness direction are formed, and the electrode pad is formed by the internal wiring pattern and the via hole conductor. 24 and 24 are led out via the via-hole conductor 236 to the crystal vibrator lead-out electrodes 232 and 232 formed in the upper part of the opening end face of the crystal vibrator mounting substrate 2 shown in FIG.
[0020]
Further, an oscillation circuit derivation electrode 234 is formed at the corner of the opening end face on the upper surface of the container side wall of the crystal resonator mounting substrate 2 shown in FIG. 3A, and the oscillation circuit derivation electrode 234 is the crystal resonator mounting substrate. 2 are connected to terminal electrodes 26, 26, 26, 26 for surface mounting formed at the four corners of the back surface of 2 via end faces. Reference numeral 233 denotes a ground electrode, which is connected to a sealing conductor 221 formed around the inner periphery of the upper surface of the dielectric substrate 22.
[0021]
The sealing conductor film 221 is formed by depositing a metallized layer such as tungsten or molybdenum, and further, Ni and Au are plated on the surface thereof. Further, the crystal oscillator lead electrodes 232 and 232, and electrode pads 233 and 234 such as a ground electrode are formed by baking a conductive resin paste, and then Ni is formed by plating, and Au plating is further formed on the upper surface. .
[0022]
The quartz resonator 3 includes a strip-shaped quartz substrate 30 cut with a predetermined crystal axis (AT cut), a pair of excitation electrodes 31 and 31 formed on both main surfaces of the quartz substrate 30, and the excitation electrodes 31 and 31. The lead electrode 32 extends to one end of the quartz substrate 30. Such excitation electrodes 31 and extraction electrodes 32 are formed of Au, Ag, Cr, or the like by using a means such as vapor deposition or sputtering by arranging a mask having a predetermined shape on the upper and lower surfaces of the quartz substrate 30.
The metal lid 6 is a metal plate made of, for example, an Fe—Ni alloy (42 alloy), an Fe—Ni—Co alloy (Kovar), or the like, and a brazing material layer is formed at least on the joining surface side. Examples of the layer include Au alloy, Sn, solder, and aluminum alloy. Further, a plating layer such as Ni or Au is formed on the surface where the brazing material layer is not formed. The metal lid 6 is hermetically sealed by injecting nitrogen gas or the like into the cavity 20 or by seam welding together with the sealing conductor film 221 in a vacuum.
[0023]
The oscillation circuit substrate 7 is formed by laminating a dielectric substrate 71 and a dielectric substrate 72 provided around the dielectric substrate 71.
[0024]
An internal wiring pattern 725 is formed between the laminated dielectric substrate 71 and the dielectric substrate 72, and the IC chip 8 and the electronic component element 9 constitute a circuit of the oscillation circuit substrate 7 by the internal wiring pattern 725. Then, a part of the internal wiring pattern is drawn out and connected to electrode pads 722, 723, and 724 formed on the upper surface of the opening of the ring-shaped ceramic layer 72. End face electrodes 727 connected to the plurality of ground electrodes 724 are formed from the dielectric substrate 72 to the dielectric substrate 71.
[0025]
Further, a ground electrode 73 is formed on the entire surface of the oscillation circuit substrate 7 opposite to the opening, and is connected to the ground electrode 723 formed on the upper surface around the container. The electrode pads 722 and 724 and the ground electrode 723 formed in the opening are connected to the crystal oscillator lead electrode 234, the crystal vibrator lead electrode 232, and the electrode pad 233 on the upper surface of the crystal vibrator mounting substrate 2 opening.
[0026]
The IC chip 8 is a circuit component in which a circuit for exciting the crystal unit 3 is integrated. An IC connection electrode (not shown) formed on the bottom surface of the cavity of the oscillation circuit substrate 7 is connected to, for example, an Au bump 7a. Are connected by a method such as flip chip. Specifically, the IC chip 7 is connected by bonding or pasting an Ag paste to be the Au bump 7a by adhesion or ultrasonic waves. Further, as shown in FIG. 1, a thermosetting resin 74 covering the IC chip 8 may be formed, or at least the thermosetting resin 74 is filled between the cavity bottom surface of the ceramic substrate 71 and the IC chip back surface. good. The thermosetting resin 74 is reinforced in terms of the bonding strength between the IC chip 8 and the oscillation circuit substrate 7 by heat curing. As the thermosetting resin 74, for example, an epoxy resin is used.
[0027]
Further, the quartz crystal resonator mounting substrate 2 and the oscillation circuit substrate 7 are arranged so that the openings face each other, and are connected by using a conductive resin paste that is cured to become a conductive adhesive member. The transducer lead-out electrodes 232 and 232 and the electrode pads 722 and 722, and further the electrode pads 233 and 234 and the electrode pads 723 and 724 are arranged to correspond to each other, and are connected to each other.
[0028]
In this way, the crystal oscillator mounting substrate 2 and the oscillation circuit substrate 7 are connected to the shielded containers to form a crystal oscillator, thereby achieving a crystal oscillator with improved shielding effect.
[0029]
As another example, as shown in FIG. 5, a ground electrode 125 is formed on the entire surface opposite to the cavity 120 of the crystal resonator mounting substrate 2, while the cavity of the oscillation circuit substrate container 17 Electrode pads 176 may be formed on the opposite surface, and the upper and lower main surfaces may be oppositely positioned relative to the example shown in FIGS.
The electrical / mechanical connection between the crystal oscillator mounting substrate 2 and the open end face of the oscillation circuit substrate 7 is performed by a conductive resin paste (not shown) that is cured to become a conductive adhesive member.
[0030]
The above-described crystal oscillator 1 is manufactured as follows.
First, a strip-shaped quartz substrate 3 is prepared. Next, the excitation electrodes 31 are formed on both main surfaces of the quartz substrate 30, and the extraction electrodes 32 led out from the excitation electrode 31 are formed on both surfaces of the quartz substrate 30, thereby producing the quartz crystal resonator 3.
[0031]
Next, a crystal resonator mounting substrate 2 is prepared in which a cavity 20 is formed on one main surface, and a pair of electrode pads 24 and 24 are formed by plating on the bottom surface, that is, one main surface of the dielectric substrate 21. In the crystal resonator container, dielectric substrates 22 and 23 are laminated on one main surface of the dielectric substrate 21, and a sealing conductor film 221 is formed on the inner peripheral upper surface of the dielectric substrate 22. The other dielectric substrate 23 has electrode pads 232, 233, 234 and the like formed on the upper surface.
[0032]
Next, for example, a conductive resin paste that hardens to become the conductive adhesive member 4 is supplied and applied to the electrode pads 24 and 24 with a dispenser or the like. At this time, the supplied conductive resin paste has a generally hemispherical shape.
[0033]
Then, it is placed on the conductive resin paste so that the extraction electrodes 32, 32 of the crystal unit 3 are in contact with each other. Next, the conductive resin paste is cured, and the ceramic package 2 and the crystal unit 3 are cured by heat to be bonded and fixed.
[0034]
Next, the frequency of the crystal unit 3 is adjusted. Specifically, electrode pads for oscillation frequency measurement (not shown) are formed on the electrode pads 232 and 232 formed on the opening end face of the crystal resonator mounting substrate 2, and a power supply voltage, ground and frequency measurement probe is formed. The oscillation frequency is adjusted by increasing or decreasing the mass of the excitation electrode by Ag vapor deposition or ion gun on the excitation electrode of the crystal resonator 3 in a state where the crystal resonator 3 is oscillated.
Next, the metal lid 6 is placed on the sealing conductor film 221 in a predetermined atmosphere such as N2 or He so that the joint surface faces downward, and both are sealed by seam welding.
Next, the IC chip 8 is mounted on one main surface of the oscillation circuit board 7. Specifically, Au bumps (not shown) formed on the IC chip 8 and electrode pads (not shown) formed on the main surface of the ceramic substrate 71 are first positioned and placed at corresponding positions. Thereafter, the IC chips 8 are bonded to each other by bonding with Ag paste or fusion with ultrasonic waves.
Next, an epoxy thermosetting resin 74 is filled so as to cover the IC chip 8 and is heated and cured.
[0035]
Finally, the crystal resonator mounting substrate 2 and the oscillation circuit substrate 7 are disposed so that the respective openings face each other, and the electrode pads 232 and 232, the electrode pads 722 and 722, the electrode pads 233 and 234, and the electrode pads 723 and 724 correspond to each other. The quartz crystal resonator mounting substrate 2 and the oscillation circuit substrate 7 are connected and heated using a conductive resin paste or the like that is cured to become a conductive adhesive member in a state of being positioned at the position where the substrate is positioned.
[0036]
【The invention's effect】
According to the configuration of the present invention, the cavity-side opening of each container of the piezoelectric mounting substrate and the oscillation circuit substrate is connected to face each other, so that the piezoelectric vibrator mounting substrate and the oscillation circuit substrate are mounted between the piezoelectric vibrator mounting substrate and the oscillation circuit substrate. Since the metal lid for hermetically sealing the piezoelectric vibrator is interposed and the metal lid is connected to the ground potential, the electronic component for driving the piezoelectric vibrator and the piezoelectric vibrator Will be shielded. Accordingly, it is possible to prevent electromagnetic waves generated from electronic components that drive the piezoelectric vibrator with a simple configuration from interfering with the piezoelectric vibrator, and it is possible to provide a piezoelectric device with increased reliability.
[0037]
Further, in the present invention, since the cavity side openings of the containers are connected to face each other, the boundary between the cavities can be made a structure in which no exposed electrode is arranged because of a metal lid that is a shield electrode, and thus, stray capacitance is generated. I don't have to.
[0038]
The first connection electrode connected from the electrode pad is exposed on the upper surface of the side wall of the container of the piezoelectric vibrator mounting substrate, and the second connection is connected to the upper surface of the side wall of the container of the oscillation circuit substrate from the internal wiring. An electrode is formed, and the piezoelectric vibrator mounting substrate and the oscillation circuit substrate are connected to each other by adopting a configuration in which the first connection electrode and the second connection electrode are brought into contact with each other. Electrical / mechanical connection and shielding effect can be achieved at the same time by simply connecting the openings on the container cavity side of the substrate and the oscillation circuit substrate so as to face each other, increasing mass productivity and improving yield. .
[0039]
Furthermore, in the present invention, since the cavity side openings of the respective containers are connected to face each other, when a piezoelectric device is mounted on the main substrate, the surface thereof is susceptible to electromagnetic influence from the outside. Then, since the surface of the main board on which the piezoelectric device is mounted is always covered with the ground electrode, the metal lid is connected to the ground potential to prevent electromagnetic interference from the internal electronic components and Electrical interference from the outside can be shielded by the ground electrode, and a highly reliable piezoelectric device can be provided.
[Brief description of the drawings]
FIG. 1 is a side sectional view of a piezoelectric device of the present invention.
2A is a side cross-sectional view of only a crystal resonator mounting substrate used in a piezoelectric device, and FIG. 2B is a side view of only a transmission circuit substrate.
3A is a top view in which a lid of a crystal resonator used in the piezoelectric device of the present invention is omitted, and FIG. 3B is a bottom view of the crystal resonator used in the piezoelectric device of the present invention. .
4A is a top view of an oscillation circuit board used in the piezoelectric device of the present invention, and FIG. 4B is a bottom view of the oscillation circuit board used in the piezoelectric device of the present invention.
FIG. 5 is a side sectional view showing another example of the piezoelectric device of the present invention.
FIG. 6 is an exploded side sectional view of a conventional piezoelectric device.
FIG. 7 is a top view in which a lid of a conventional piezoelectric device is omitted.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Crystal oscillator 2 ... Crystal resonator mounting substrate 20 ... Cavity 21 ... Dielectric substrate 221 ... Sealing conductor film 24 ... External terminal electrode 3 ... Crystal resonator 30 ... Quartz substrate 4 ... Conductive adhesive member 6 ... Metal lid 7 ... Oscillation circuit board 73 ... Earth electrode 8 ... IC chip

Claims (2)

On the other hand, a rectangular container having a cavity formed on the main surface, a plurality of electrode pads formed on the bottom surface of the cavity, a piezoelectric vibrator having a pair of excitation electrodes connected to the electrode pads, and the cavity A piezoelectric vibrator mounting substrate having a metal lid for sealing;
On the other hand, an oscillation circuit board having a rectangular container having a cavity formed on the main surface, an internal wiring formed on the bottom surface of the cavity, and an electronic component connected to the internal wiring and driving the piezoelectric vibrator And consist of
Electrically connecting one main surface side of the piezoelectric vibrator mounting substrate and one main surface side of the oscillation circuit substrate to each other electrically and mechanically, and connecting the metal lid to a ground potential ;
The container of the piezoelectric vibrator mounting substrate includes a ring-shaped first substrate and a ring-shaped second substrate having a larger inner circumference than the first substrate and having a narrow width,
The oscillation circuit board includes a ring-shaped third substrate having a smaller inner circumference and a wider width than the second substrate;
The piezoelectric device is characterized in that the metal lid is surrounded by the second substrate and located between the first substrate and the third substrate . The piezoelectric device according to claim 1, wherein the metal lid is bonded to the first substrate.

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